Question

An unknown quantity of gas is held at a temperature of 295 K in a container with a volume of 25 L and a pressure of 742 kPa. How many moles of gas are in the container?

Answer 1

Using PV = nRT you can rearrange to find n = PV/RT
P = 742000 Pa
V = 0.025 m^3
R = 8.31
T = 295 K

n = (742000 • 0.025)/(8.31 • 295)
n = 7.56 mol

Answer 2

7.56 moles

Step-by-step explanation:

For a 742 kPa, we can consider the gas as an ideal gas because it will be close to 7 atm (1 kPa = 0.01 atm), which is low pressure. So, the ideal gas equation is:

PV = nRT

Where P is the pressure, V is the volume, n the number of moles, R the gas constant and T the temperature (always in Kelvin). For pressure in kPa and volume in liters, R = 8.314 kPa.L/mol.K, then:

742x25 = nx8.314x295

2452.63n = 18550

n = 18550/2452.63

n = 7.56 moles